Do Races Differ? Not
Really, DNA Shows

New York Times August 22, 2000

By NATALIE ANGIER

In these glossy, lightweight
days of an election year, it seems, they can't build metaphorical
tents big or fast enough for every politician who wants to pitch
one up and invite the multicultural folds to "Come on under!"
The feel-good message that both parties seek to convey is: regardless
of race or creed, we really ARE all kin beneath the skin.

Yet whatever the calculated
quality of this new politics of inclusion, its sentiment accords
firmly with scientists' growing knowledge of the profound genetic
fraternity that binds together human beings of the most seemingly
disparate origins.

Scientists have long suspected
that the racial categories recognized by society are not reflected
on the genetic level.

But the more closely that
researchers examine the human genome -the complement of genetic
material encased in the heart of almost every cell of the body
-- the more most of them are convinced that the standard labels
used to distinguish people by "race" have little or
no biological meaning.

They say that while it may
seem easy to tell at a glance whether a person is Caucasian,
African or Asian, the ease dissolves when one probes beneath
surface characteristics and scans the genome for DNA hallmarks
of "race."

As it turns out, scientists
say, the human species is so evolutionarily young, and its migratory
patterns so wide, restless and rococo, that it has simply not
had a chance to divide itself into separate biological groups
or "races" in any but the most superficial ways.

"Race is a social concept,
not a scientific one," said Dr.

J. Craig Venter, head of the
Celera Genomics Corporation in Rockville, Md. "We all evolved
in the last 100,000 years from the same small number of tribes
that migrated out of Africa and colonized the world."

Dr. Venter and scientists
at the National Institutes of Health recently announced that
they had put together a draft of the entire sequence of the human
genome, and the researchers had unanimously declared, there is
only one race -- the human race.

Dr. Venter and other researchers
say that those traits most commonly used to distinguish one
race from another, like skin and eye color, or the width of
the nose, are traits controlled by a relatively few number of
genes, and thus have been able to change rapidly in response
to extreme environmental pressures during the short course of
Homo sapiens history.

And so equatorial populations
evolved dark skin, presumably to protect against ultraviolet
radiation, while people in northern latitudes evolved pale skin,
the better to produce vitamin D from pale sunlight.

"If you ask what percentage
of your genes is reflected in your external appearance, the basis
by which we talk about race, the answer seems to be in the range
of .01 percent," said Dr.

Harold P. Freeman, the chief
executive, president and director of surgery at North General
Hospital in Manhattan, who has studied the issue of biology and
race. "This is a very, very minimal reflection of your genetic
makeup."

Unfortunately for social harmony,
the human brain is exquisitely attuned to differences in packaging
details, prompting people to exaggerate the significance of what
has come to be called race, said Dr. Douglas C. Wallace, a professor
of molecular genetics at Emory University School of Medicine
in Atlanta.

"The criteria that people
use for race are based entirely on external features that we
are programmed to recognize," he said.

"And the reason we're
programmed to recognize them is that it's vitally important to
our species that each of us be able to distinguish one individual
from the next.

Our whole social structure
is based on visual cues, and we've been programmed to recognize
them, and to recognize individuals."

By contrast with the tiny
number of genes that make some people dark-skinned and doe-eyed,
and others as pale as napkins, scientists say that traits like
intelligence, artistic talent and social skills are likely to
be shaped by thousands, if not tens of thousands, of the 80,000
or so genes in the human genome, all working in complex combinatorial
fashion.

The possibility of such gene
networks shifting their interrelationships wholesale in the course
of humanity's brief foray across the globe, and being skewed
in significant ways according to "race" is "a
bogus idea," said Dr. Aravinda Chakravarti, a geneticist
at Case Western University in Cleveland.

"The differences that
we see in skin color do not translate into widespread biological
differences that are unique to groups."

Dr. Jurgen K. Naggert, a
geneticist at the Jackson Laboratory in Bar Harbor, Me., said:
"These big groups that we characterize as races are too
heterogeneous to lump together in a scientific way.

If you're doing a DNA study
to look for markers for a particular disease, you can't use 'Caucasians'
as a group. They're too diverse.

No journal would accept it."

Yet not every researcher sees
race as a meaningless or antediluvian notion.

"I think racial classifications
have been useful to us," said Dr. Alan Rogers, a population
geneticist and professor of anthropology at the University of
Utah in Salt Lake City. "We may believe that most differences
between races are superficial, but the differences are there,
and they are informative about the origins and migrations of
our species. To do my work, I have to get genetic data from
different parts of the world, and look at differences within
groups and between groups, so it helps to have labels for groups."

"We may believe that most
differences between races are superficial, but differences are
there." Dr. Alan Rogers Population geneticist and professor
of anthropology, University of Utah And there are a handful of
researchers who continue to insist that there are fundamental
differences among the three major races that extend to the brain.

Dr. J. Philippe Rushton,
a psychologist at University of Western Ontario in Canada and
author of "Race, Evolution and Behavior," is perhaps
the most tireless proponent of the belief that the three major
races differ genetically in ways that affect average group I.Q.
and a propensity toward criminal behavior.

He asserts that his work reveals
east Asians to have the largest average brain size and intelligence
scores, those of African descent to have the smallest average
brains and I.Q.'s, and those of European ancestry to fall in
the middle.

Yet many scientists have objected
to his methods and interpretations, arguing, among other things,
that the link between total brain size and intelligence is
far from clear. Women, for example, have smaller brains than
men do, even when adjusted for their comparatively smaller body
mass, yet average male and female I.Q. scores are the same.

For that matter, fossil evidence
suggests that Neanderthals had very sizable brains, and they
did not even last long enough to invent standardized tests.

Dr. Eric S. Lander, a genome
expert at the Whitehead Institute in Cambridge, Mass., admits
that, because research on the human genome has just begun, he
cannot deliver a definitive, knockout punch to those who would
argue that significant racial differences must be reflected somewhere
in human DNA and will be found once researchers get serious
about looking for them. But as Dr.

Lander sees it, the proponents
of such racial divides are the ones with the tough case to defend.

"There's no scientific
evidence to support substantial differences between groups,"
he said, "and the tremendous burden of proof goes to anyone
who wants to assert those differences."

Although research into the
structure and sequence of the human genome is in its infancy,
geneticists have pieced together a rough outline of human genomic
history, variously called the "Out of Africa" or "Evolutionary
Eve" hypothesis.

By this theory, modern Homo
sapiens originated in Africa 200,000 to 100,000 years ago, at
which point a relatively small number of them, maybe 10,000
or so, began migrating into the Middle East, Europe, Asia and
across the Bering land mass into the Americas. As they traveled,
they seem to have completely or largely displaced archaic humans
already living in the various continents, either through calculated
acts of genocide, or simply outreproducing them into extinction.

Since the African emigrations
began, a mere 7,000 generations have passed. And because the founding
population of &#0233;migr&#0233;s was small, it could
only take so much genetic variation with it.

As a result of that combination
-- a limited founder population and a short time since dispersal
-- humans are strikingly homogeneous, differing from one another
only once in a thousand subunits of the genome.

"We are a small population
grown large in the blink of an eye," Dr. Lander said.

"We are a little village
that's grown all over the world, and we retain the genetic variation
seen in that little village."

The human genome is large,
though, composed of three billion-odd subunits, or bases, which
means that even a tiny percentage of variation from one individual
to the next amounts to a sizable number of genetic discrepancies.

The question is, where in
the genome is that variation found, and how is it distributed
among different populations?

Through transglobal sampling
of neutral genetic markers -stretches of genetic material that
do not help create the body's functioning proteins but instead
are composed of so-called junk DNA -- researchers have found
that, on average, 88 percent to 90 percent of the differences
between people occur within their local populations, while only
about 10 percent to 12 percent of the differences distinguish
one population, or race, from another.

To put it another way, the
citizens of any given village in the world, whether in Scotland
or Tanzania, hold 90 percent of the genetic variability that
humanity has to offer.

But that 90/10 ratio is just
an average, and refers only to junk-DNA markers.

For the genetic material that
encodes proteins, the picture is somewhat more complex. Many
workhorse genes responsible for basic organ functions show virtually
no variability from individual to individual, which means they
are even less "race specific" than are neutral genetic
markers.

Some genes, notably those
of the immune system, show enormous variability, but the variability
does not track with racial groupings. Then there are the genes
that control pigmentation and other physical features.

These also come in a wide
assortment of "flavors," but unlike immune-related genes,
are often distributed in population-specific clusters, resulting
in Swedes who look far more like other Swedes than they do like
Australian Aborigines.

A few group differences are
more than skin deep.

Among the most famous examples
are the elevated rates of sickle-cell anemia among African-Americans
and of beta-thalassemia, another hemoglobin disorder, among those
of Mediterranean heritage.

Both traits evolved to help
the ancestors of these groups resist malaria infection, but both
prove lethal when inherited in a double dose. As with differences
in skin pigmentation, the pressure of the environment to develop
a group-wide trait was powerful, and the means to do so simple
and straightforward, through the alteration of a single gene.

The University of Utah

"If you ask what percentage
of your genes is reflected in your external appearance, the basis
by which we talk about race, the answer seems to be in the range
of .01 percent." Dr. Harold Freeman Hospital executive and
surgeon who has studied the issue of biology and race. Another
cause of group differences is the so-called founder effect. In
such cases, the high prevalence of an unusual condition in a
population can be traced to a founding ancestor who happened
to carry a novel mutation into the region.

Over many generations of comparative
isolation and inbreeding, the community, like it or not, became
"enriched" with the founder's disorder. The founder
effect explains the high incidence of Huntington's neurodegenerative
disease in the Lake Maracaibo region of Venezuela, and of Tay-Sachs
disease among Ashkenazi Jews.

But Dr. Naggert emphasized
that medical geneticists had a much better chance of unearthing
these founder effects by scrutinizing small, isolated and well-defined
populations, like the northern Finns, the Basques of Spain, or
the Amish of Pennsylvania, than they did by going after "races."

Dr. Sonia S. Anand, an assistant
professor of medicine at McMaster University in Ontario, proposed
that clinicians think about ethnicity rather than race when seeking
clues to how disease patterns differ from one group to the next.

"Ethnicity is a broad
concept that encompasses both genetics and culture," Dr.
Anand said. "Thinking about ethnicity is a way to bring
together questions of a person's biology, lifestyle, diet, rather
than just focusing on race. Ethnicity is about phenotype and
genotype, and, if you define the terms of your study, it allows
you to look at differences between groups in a valid way."

In investigating the reasons
behind the high incidence of cardiovascular disease among people
from the Indian subcontinent, for example, Dr. Anand discovered
that Indians had comparatively elevated amounts of clotting
factors in their blood.

Beyond tallying up innate
traits, she also takes into account how Indian culture and life
habits may pose added risks for heart disease -- noting, for
example, that a woman's status in India is directly proportional
to her number of belly rolls.

In Dr. Freeman's view, the
science of human origins can help to heal any number of wounds,
and that, he says is sweet justice.

"Science got us into
this problem in the first place, with its measurements of skulls
and its emphasis on racial differences and racial classifications,"
Dr. Freeman said.

"Scientists should now
get us out of it. They need to be leaders in promoting an evolutionary
understanding of the human race."